Re: [PATCH bpf-next v4 1/3] libbpf: Introduce bpf_program__clone()

["Emil Tsalapatis" <emil@etsalapatis.com>]

On Tue Mar 17, 2026 at 1:39 PM EDT, Mykyta Yatsenko wrote:
> From: Mykyta Yatsenko <yatsenko@meta.com>
>
> Add bpf_program__clone() API that loads a single BPF program from a
> prepared BPF object into the kernel, returning a file descriptor owned
> by the caller.
>
> After bpf_object__prepare(), callers can use bpf_program__clone() to
> load individual programs with custom bpf_prog_load_opts, instead of
> loading all programs at once via bpf_object__load(). Non-zero fields in
> opts override the defaults derived from the program and object
> internals; passing NULL opts populates everything automatically.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>

Overriding the prepare_load_fn() callback's results with user-provided
ones is a valid choice design-wise.

> ---
>  tools/lib/bpf/libbpf.c   | 78 ++++++++++++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   | 17 +++++++++++
>  tools/lib/bpf/libbpf.map |  1 +
>  3 files changed, 96 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 0662d72bad20..1eaa7527d4da 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9802,6 +9802,84 @@ __u32 bpf_program__line_info_cnt(const struct bpf_program *prog)
>  	return prog->line_info_cnt;
>  }
>  
> +int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts *opts)
> +{
> +	LIBBPF_OPTS(bpf_prog_load_opts, attr);
> +	struct bpf_object *obj;
> +	int err, fd;
> +
> +	if (!prog)
> +		return libbpf_err(-EINVAL);
> +
> +	if (!OPTS_VALID(opts, bpf_prog_load_opts))
> +		return libbpf_err(-EINVAL);
> +
> +	obj = prog->obj;
> +	if (obj->state < OBJ_PREPARED)
> +		return libbpf_err(-EINVAL);
> +
> +	/*
> +	 * Caller-provided opts take priority; fall back to
> +	 * prog/object defaults when the caller leaves them zero.
> +	 */
> +	attr.attach_prog_fd = OPTS_GET(opts, attach_prog_fd, 0) ?: prog->attach_prog_fd;
> +	attr.prog_flags = OPTS_GET(opts, prog_flags, 0) ?: prog->prog_flags;
> +	attr.prog_ifindex = OPTS_GET(opts, prog_ifindex, 0) ?: prog->prog_ifindex;
> +	attr.kern_version = OPTS_GET(opts, kern_version, 0) ?: obj->kern_version;
> +	attr.fd_array = OPTS_GET(opts, fd_array, NULL) ?: obj->fd_array;
> +	attr.fd_array_cnt = OPTS_GET(opts, fd_array_cnt, 0) ?: obj->fd_array_cnt;
> +	attr.token_fd = OPTS_GET(opts, token_fd, 0) ?: obj->token_fd;
> +	if (attr.token_fd)
> +		attr.prog_flags |= BPF_F_TOKEN_FD;
> +
> +	/* BTF func/line info */
> +	if (obj->btf && btf__fd(obj->btf) >= 0) {
> +		attr.prog_btf_fd = OPTS_GET(opts, prog_btf_fd, 0) ?: btf__fd(obj->btf);
> +		attr.func_info = OPTS_GET(opts, func_info, NULL) ?: prog->func_info;
> +		attr.func_info_cnt = OPTS_GET(opts, func_info_cnt, 0) ?: prog->func_info_cnt;
> +		attr.func_info_rec_size =
> +			OPTS_GET(opts, func_info_rec_size, 0) ?: prog->func_info_rec_size;
> +		attr.line_info = OPTS_GET(opts, line_info, NULL) ?: prog->line_info;
> +		attr.line_info_cnt = OPTS_GET(opts, line_info_cnt, 0) ?: prog->line_info_cnt;
> +		attr.line_info_rec_size =
> +			OPTS_GET(opts, line_info_rec_size, 0) ?: prog->line_info_rec_size;
> +	}
> +
> +	attr.log_buf = OPTS_GET(opts, log_buf, NULL);
> +	attr.log_size = OPTS_GET(opts, log_size, 0);
> +	attr.log_level = OPTS_GET(opts, log_level, 0);
> +
> +	/*
> +	 * Fields below may be mutated by prog_prepare_load_fn:
> +	 * Seed them from prog/obj defaults here;
> +	 * Later override with caller-provided opts.
> +	 */
> +	attr.expected_attach_type = prog->expected_attach_type;
> +	attr.attach_btf_id = prog->attach_btf_id;
> +	attr.attach_btf_obj_fd = prog->attach_btf_obj_fd;
> +
> +	if (prog->sec_def && prog->sec_def->prog_prepare_load_fn) {
> +		err = prog->sec_def->prog_prepare_load_fn(prog, &attr, prog->sec_def->cookie);
> +		if (err)
> +			return libbpf_err(err);
> +	}
> +
> +	/* Re-apply caller overrides for output fields */
> +	if (OPTS_GET(opts, expected_attach_type, 0))
> +		attr.expected_attach_type =
> +			OPTS_GET(opts, expected_attach_type, 0);
> +	if (OPTS_GET(opts, attach_btf_id, 0))
> +		attr.attach_btf_id = OPTS_GET(opts, attach_btf_id, 0);
> +	if (OPTS_GET(opts, attach_btf_obj_fd, 0))
> +		attr.attach_btf_obj_fd =
> +			OPTS_GET(opts, attach_btf_obj_fd, 0);
> +
> +	fd = bpf_prog_load(prog->type, prog->name, obj->license, prog->insns, prog->insns_cnt,
> +			   &attr);
> +
> +	return libbpf_err(fd);
> +}
> +
>  #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {			    \
>  	.sec = (char *)sec_pfx,						    \
>  	.prog_type = BPF_PROG_TYPE_##ptype,				    \
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index dfc37a615578..0be34852350f 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -2021,6 +2021,23 @@ LIBBPF_API int libbpf_register_prog_handler(const char *sec,
>   */
>  LIBBPF_API int libbpf_unregister_prog_handler(int handler_id);
>  
> +/**
> + * @brief **bpf_program__clone()** loads a single BPF program from a prepared
> + * BPF object into the kernel, returning its file descriptor.
> + *
> + * The BPF object must have been previously prepared with
> + * **bpf_object__prepare()**. If @opts is provided, any non-zero field
> + * overrides the defaults derived from the program/object internals.
> + * If @opts is NULL, all fields are populated automatically.
> + *
> + * The returned FD is owned by the caller and must be closed with close().
> + *
> + * @param prog BPF program from a prepared object
> + * @param opts Optional load options; non-zero fields override defaults
> + * @return program FD (>= 0) on success; negative error code on failure
> + */
> +LIBBPF_API int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts *opts);
> +
>  #ifdef __cplusplus
>  } /* extern "C" */
>  #endif
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index d18fbcea7578..e727a54e373a 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -452,6 +452,7 @@ LIBBPF_1.7.0 {
>  		bpf_map__set_exclusive_program;
>  		bpf_map__exclusive_program;
>  		bpf_prog_assoc_struct_ops;
> +		bpf_program__clone;
>  		bpf_program__assoc_struct_ops;
>  		btf__permute;
>  } LIBBPF_1.6.0;